"I would contend that there is no trademark violation, as permission for minor modifications to the source of Ion3 is implied by distributing the source."

I thought it was understood that if you modify someone's GPL'ed source, you either a) submit it back to the original author for acceptance b) fork the code or c) keep it for private/internal use. In this respect, Tuomo's anger seems justified. It's a pity that he feels he needs to lash out when the solution is simple. Politely ask your offender to rename their project. I would also think he has a case for GPL violation, but as I said earlier, I thought respect was understood.

Respect the author, respect the code.
Full disclosure: I'm a fan of Ion3.